<template>
  <view>
    <view class="wrapper">
      <view class="handBtn">
        <button @tap="retDraw" class="delBtn">重写</button>
        <button @tap="subCanvas" class="subBtn">完成</button>
      </view>
      <view class="handCenter">
        <canvas class="handWriting" :disable-scroll="true" @touchstart="uploadScaleStart" @touchmove="uploadScaleMove"
          @touchend="uploadScaleEnd" canvas-id="handWriting"></canvas>
      </view>
      <view class="handRight">
        <view class="handTitle">请签名</view>
      </view>
    </view>
  </view>
</template>

<script>
  export default {
    data() {
      return {
        canvasName: 'handWriting',
        ctx: '',
        canvasWidth: 0,
        canvasHeight: 0,
        transparent: 1, // 透明度
        selectColor: 'black',
        lineColor: '#1A1A1A', // 颜色
        lineSize: 1.5, // 笔记倍数
        lineMin: 0.5, // 最小笔画半径
        lineMax: 4, // 最大笔画半径
        pressure: 1, // 默认压力
        smoothness: 60, //顺滑度，用60的距离来计算速度
        currentPoint: {},
        currentLine: [], // 当前线条
        firstTouch: true, // 第一次触发
        radius: 1, //画圆的半径
        cutArea: {
          top: 0,
          right: 0,
          bottom: 0,
          left: 0
        }, //裁剪区域
        bethelPoint: [], //保存所有线条 生成的贝塞尔点；
        lastPoint: 0,
        chirography: [], //笔迹
        currentChirography: {}, //当前笔迹
        linePrack: [] //划线轨迹 , 生成线条的实际点
      };
    },
    onLoad() {
      uni.showToast({
        title:'请必须是本人名字，协议才可生效',
        icon:'none',
        duration: 3000,
       })
      let canvasName = this.canvasName;
      let ctx = wx.createCanvasContext(canvasName);

      this.ctx = ctx;
      var query = wx.createSelectorQuery();
      query
        .select('.handCenter')
        .boundingClientRect(rect => {
          this.canvasWidth = rect.width;
          this.canvasHeight = rect.height;

          /* 将canvas背景设置为 白底，不设置  导出的canvas的背景为透明 */

        })
        .exec();
    },
    methods: {
      // 笔迹开始
      uploadScaleStart(e) {
        if (e.type != 'touchstart') return false;
        let ctx = this.ctx;
        ctx.setFillStyle(this.lineColor); // 初始线条设置颜色
        ctx.setGlobalAlpha(this.transparent); // 设置半透明
        let currentPoint = {
          x: e.touches[0].x,
          y: e.touches[0].y
        };
        let currentLine = this.currentLine;
        currentLine.unshift({
          time: new Date().getTime(),
          dis: 0,
          x: currentPoint.x,
          y: currentPoint.y
        });
        this.currentPoint = currentPoint;
        // currentLine
        if (this.firstTouch) {
          this.cutArea = {
            top: currentPoint.y,
            right: currentPoint.x,
            bottom: currentPoint.y,
            left: currentPoint.x
          };
          this.firstTouch = false;
        }
        this.pointToLine(currentLine);
      },
      // 笔迹移动
      uploadScaleMove(e) {
        if (e.type != 'touchmove') return false;
        if (e.cancelable) {
          // 判断默认行为是否已经被禁用
          if (!e.defaultPrevented) {
            e.preventDefault();
          }
        }
        let point = {
          x: e.touches[0].x,
          y: e.touches[0].y
        };

        //测试裁剪
        if (point.y < this.cutArea.top) {
          this.cutArea.top = point.y;
        }
        if (point.y < 0) this.cutArea.top = 0;

        if (point.x > this.cutArea.right) {
          this.cutArea.right = point.x;
        }
        if (this.canvasWidth - point.x <= 0) {
          this.cutArea.right = this.canvasWidth;
        }
        if (point.y > this.cutArea.bottom) {
          this.cutArea.bottom = point.y;
        }
        if (this.canvasHeight - point.y <= 0) {
          this.cutArea.bottom = this.canvasHeight;
        }
        if (point.x < this.cutArea.left) {
          this.cutArea.left = point.x;
        }
        if (point.x < 0) this.cutArea.left = 0;

        this.lastPoint = this.currentPoint;
        this.currentPoint = point;

        let currentLine = this.currentLine;
        currentLine.unshift({
          time: new Date().getTime(),
          dis: this.distance(this.currentPoint, this.lastPoint),
          x: point.x,
          y: point.y
        });

        this.pointToLine(currentLine);
      },
      // 笔迹结束
      uploadScaleEnd(e) {
        if (e.type != 'touchend') return 0;
        let point = {
          x: e.changedTouches[0].x,
          y: e.changedTouches[0].y
        };
        this.lastPoint = this.currentPoint;
        this.currentPoint = point;

        let currentLine = this.currentLine;
        currentLine.unshift({
          time: new Date().getTime(),
          dis: this.distance(this.currentPoint, this.lastPoint),
          x: point.x,
          y: point.y
        });

        if (currentLine.length > 2) {
          var info = (currentLine[0].time - currentLine[currentLine.length - 1].time) / currentLine.length;
          //$("#info").text(info.toFixed(2));
        }
        //一笔结束，保存笔迹的坐标点，清空，当前笔迹
        //增加判断是否在手写区域；
        this.pointToLine(currentLine);
        var currentChirography = {
          lineSize: this.lineSize,
          lineColor: this.lineColor
        };
        var chirography = this.chirography;
        chirography.unshift(currentChirography);
        this.chirography = chirography;

        var linePrack = this.linePrack;
        linePrack.unshift(this.currentLine);
        this.linePrack = linePrack;
        this.currentLine = [];
      },
      retDraw() {
        this.ctx.clearRect(0, 0, 700, 730);
        this.ctx.draw();

        //设置canvas背景
        this.setCanvasBg('#fff');
      },
      //画两点之间的线条；参数为:line，会绘制最近的开始的两个点；
      pointToLine(line) {
        this.calcBethelLine(line);
        return;
      },
      //计算插值的方式；
      calcBethelLine(line) {
        if (line.length <= 1) {
          line[0].r = this.radius;
          return;
        }
        let x0,
          x1,
          x2,
          y0,
          y1,
          y2,
          r0,
          r1,
          r2,
          len,
          lastRadius,
          dis = 0,
          time = 0,
          curveValue = 0.5;
        if (line.length <= 2) {
          x0 = line[1].x;
          y0 = line[1].y;
          x2 = line[1].x + (line[0].x - line[1].x) * curveValue;
          y2 = line[1].y + (line[0].y - line[1].y) * curveValue;
          //x2 = line[1].x;
          //y2 = line[1].y;
          x1 = x0 + (x2 - x0) * curveValue;
          y1 = y0 + (y2 - y0) * curveValue;
        } else {
          x0 = line[2].x + (line[1].x - line[2].x) * curveValue;
          y0 = line[2].y + (line[1].y - line[2].y) * curveValue;
          x1 = line[1].x;
          y1 = line[1].y;
          x2 = x1 + (line[0].x - x1) * curveValue;
          y2 = y1 + (line[0].y - y1) * curveValue;
        }
        //从计算公式看，三个点分别是(x0,y0),(x1,y1),(x2,y2) ；(x1,y1)这个是控制点，控制点不会落在曲线上；实际上，这个点还会手写获取的实际点，却落在曲线上
        len = this.distance({
          x: x2,
          y: y2
        }, {
          x: x0,
          y: y0
        });
        lastRadius = this.radius;
        for (let n = 0; n < line.length - 1; n++) {
          dis += line[n].dis;
          time += line[n].time - line[n + 1].time;
          if (dis > this.smoothness) break;
        }

        this.radius = Math.min((time / len) * this.pressure + this.lineMin, this.lineMax) * this.lineSize;
        line[0].r = this.radius;
        //计算笔迹半径；
        if (line.length <= 2) {
          r0 = (lastRadius + this.radius) / 2;
          r1 = r0;
          r2 = r1;
          //return;
        } else {
          r0 = (line[2].r + line[1].r) / 2;
          r1 = line[1].r;
          r2 = (line[1].r + line[0].r) / 2;
        }
        let n = 5;
        let point = [];
        for (let i = 0; i < n; i++) {
          let t = i / (n - 1);
          let x = (1 - t) * (1 - t) * x0 + 2 * t * (1 - t) * x1 + t * t * x2;
          let y = (1 - t) * (1 - t) * y0 + 2 * t * (1 - t) * y1 + t * t * y2;
          let r = lastRadius + ((this.radius - lastRadius) / n) * i;
          point.push({
            x: x,
            y: y,
            r: r
          });
          if (point.length == 3) {
            let a = this.ctaCalc(point[0].x, point[0].y, point[0].r, point[1].x, point[1].y, point[1].r, point[2].x,
              point[2]
              .y, point[2].r);
            a[0].color = this.lineColor;
            // let bethelPoint = this.bethelPoint;
            // bethelPoint = bethelPoint.push(a);
            this.bethelDraw(a, 1);
            point = [{
              x: x,
              y: y,
              r: r
            }];
          }
        }
        this.currentLine = line;
      },
      //求两点之间距离
      distance(a, b) {
        let x = b.x - a.x;
        let y = b.y - a.y;
        return Math.sqrt(x * x + y * y);
      },
      ctaCalc(x0, y0, r0, x1, y1, r1, x2, y2, r2) {
        let a = [],
          vx01,
          vy01,
          norm,
          n_x0,
          n_y0,
          vx21,
          vy21,
          n_x2,
          n_y2;
        vx01 = x1 - x0;
        vy01 = y1 - y0;
        norm = Math.sqrt(vx01 * vx01 + vy01 * vy01 + 0.0001) * 2;
        vx01 = (vx01 / norm) * r0;
        vy01 = (vy01 / norm) * r0;
        n_x0 = vy01;
        n_y0 = -vx01;
        vx21 = x1 - x2;
        vy21 = y1 - y2;
        norm = Math.sqrt(vx21 * vx21 + vy21 * vy21 + 0.0001) * 2;
        vx21 = (vx21 / norm) * r2;
        vy21 = (vy21 / norm) * r2;
        n_x2 = -vy21;
        n_y2 = vx21;
        a.push({
          mx: x0 + n_x0,
          my: y0 + n_y0,
          color: '#1A1A1A'
        });
        a.push({
          c1x: x1 + n_x0,
          c1y: y1 + n_y0,
          c2x: x1 + n_x2,
          c2y: y1 + n_y2,
          ex: x2 + n_x2,
          ey: y2 + n_y2
        });
        a.push({
          c1x: x2 + n_x2 - vx21,
          c1y: y2 + n_y2 - vy21,
          c2x: x2 - n_x2 - vx21,
          c2y: y2 - n_y2 - vy21,
          ex: x2 - n_x2,
          ey: y2 - n_y2
        });
        a.push({
          c1x: x1 - n_x2,
          c1y: y1 - n_y2,
          c2x: x1 - n_x0,
          c2y: y1 - n_y0,
          ex: x0 - n_x0,
          ey: y0 - n_y0
        });
        a.push({
          c1x: x0 - n_x0 - vx01,
          c1y: y0 - n_y0 - vy01,
          c2x: x0 + n_x0 - vx01,
          c2y: y0 + n_y0 - vy01,
          ex: x0 + n_x0,
          ey: y0 + n_y0
        });
        a[0].mx = a[0].mx.toFixed(1);
        a[0].mx = parseFloat(a[0].mx);
        a[0].my = a[0].my.toFixed(1);
        a[0].my = parseFloat(a[0].my);
        for (let i = 1; i < a.length; i++) {
          a[i].c1x = a[i].c1x.toFixed(1);
          a[i].c1x = parseFloat(a[i].c1x);
          a[i].c1y = a[i].c1y.toFixed(1);
          a[i].c1y = parseFloat(a[i].c1y);
          a[i].c2x = a[i].c2x.toFixed(1);
          a[i].c2x = parseFloat(a[i].c2x);
          a[i].c2y = a[i].c2y.toFixed(1);
          a[i].c2y = parseFloat(a[i].c2y);
          a[i].ex = a[i].ex.toFixed(1);
          a[i].ex = parseFloat(a[i].ex);
          a[i].ey = a[i].ey.toFixed(1);
          a[i].ey = parseFloat(a[i].ey);
        }
        return a;
      },
      bethelDraw(point, is_fill, color) {
        let ctx = this.ctx;
        ctx.beginPath();
        ctx.moveTo(point[0].mx, point[0].my);
        if (undefined != color) {
          ctx.setFillStyle(color);
          ctx.setStrokeStyle(color);
        } else {
          ctx.setFillStyle(point[0].color);
          ctx.setStrokeStyle(point[0].color);
        }
        for (let i = 1; i < point.length; i++) {
          ctx.bezierCurveTo(point[i].c1x, point[i].c1y, point[i].c2x, point[i].c2y, point[i].ex, point[i].ey);
        }
        ctx.stroke();
        if (undefined != is_fill) {
          ctx.fill(); //填充图形 ( 后绘制的图形会覆盖前面的图形, 绘制时注意先后顺序 )
        }
        ctx.draw(true);
      },
      selectColorEvent(str, color) {
        this.selectColor = str;
        this.lineColor = color;
      },
      //将Canvas内容转成 临时图片 --> cb 为回调函数 形参 tempImgPath 为 生成的图片临时路径
      canvasToImg(cb) {
        //这种写法移动端 出不来

        this.ctx.draw(true, () => {
          wx.canvasToTempFilePath({
            canvasId: 'handWriting',
            fileType: 'png',
            quality: 1, //图片质量
            success(res) {
              // console.log(res.tempFilePath, 'canvas生成图片地址');

              wx.showToast({
                title: '执行了吗？'
              });

              cb(res.tempFilePath);
            }
          });
        });
      },
      //完成
      subCanvas() {
        
            uni.canvasToTempFilePath({
              canvasId: 'handWriting',
              fileType: 'png',
              quality: 1, //图片质量
              success(res) {
                console.log(res)
                uni.$emit('handWriting', {
                  path: res.tempFilePath
                })
                uni.navigateBack({
                  delta: 1
                })
              }
            
           
        })
        
      },
      setCanvasBg(color) {

        /* 将canvas背景设置为 白底，不设置  导出的canvas的背景为透明 */
        //rect() 参数说明  矩形路径左上角的横坐标，左上角的纵坐标, 矩形路径的宽度, 矩形路径的高度
        //这里是 canvasHeight - 4 是因为下边盖住边框了，所以手动减了写
        this.ctx.rect(0, 0, this.canvasWidth, this.canvasHeight - 4);
        // ctx.setFillStyle('red')
        this.ctx.setFillStyle(color);
        this.ctx.fill(); //设置填充
        this.ctx.draw(); //开画
      }
    }
  };
</script>

<style>
  page {
    background: #fbfbfb;
    height: auto;
    overflow: hidden;
  }

  .wrapper {
    width: 100%;
    height: 95vh;
    margin: 30rpx 0;
    overflow: hidden;
    display: flex;
    align-content: center;
    flex-direction: row;
    justify-content: center;
    font-size: 28rpx;
  }

  .handWriting {
    background: #fff;
    width: 100%;
    height: 95vh;
  }

  .handRight {
    display: inline-flex;
    align-items: center;
  }

  .handCenter {
    border: 4rpx dashed #e9e9e9;
    flex: 5;
    overflow: hidden;
    box-sizing: border-box;
  }

  .handTitle {
    transform: rotate(90deg);
    flex: 1;
    color: #666;
  }

  .handBtn button {
    font-size: 28rpx;
  }

  .handBtn {
    height: 95vh;
    display: inline-flex;
    flex-direction: column;
    justify-content: space-between;
    align-content: space-between;
    flex: 1;
  }

  .delBtn {
    position: absolute;
    top: 250rpx;
    left: 0rpx;
    transform: rotate(90deg);
    color: #666;
  }

  .delBtn image {
    position: absolute;
    top: 13rpx;
    left: 25rpx;
  }

  .subBtn {
    position: absolute;
    bottom: 52rpx;
    left: -3rpx;
    display: inline-flex;
    transform: rotate(90deg);
    background: #008ef6;
    color: #fff;
    margin-bottom: 30rpx;
    text-align: center;
    justify-content: center;
  }

  .previewBtn {
    position: absolute;
    top: 500rpx;
    left: 0rpx;
    transform: rotate(90deg);
    color: #666;
  }
</style>
